Using Outlook for Android for personal email and calendar management
Maybe that will help you think about it. I have included 5 Microsoft 365 accounts in the Outlook app via Exchange Online. In addition, a Hotmail account and finally an IMAP account with another provider (not Microsoft).
I have read here that IMAP may be causing the problem. That's why I removed the IMAP account from the Outlook app and have had no problems since then.
Not a solution for people who urgently need their IMAP accounts, but perhaps food for thought for support.